Attorney General Eric Holder / Eric Risberg, AP

by Kevin Johnson and Raju Chebium, USA TODAY

by Kevin Johnson and Raju Chebium, USA TODAY

WASHINGTON -- The Justice Department will not attempt to challenge state laws that allow for the medical and recreational use of marijuana as long as the drug sales do not conflict with eight new federal enforcement priorities.

Those include the distribution of marijuana to minors and sales that assist or act as cover for trafficking operations, according to a directive being issued Thursday to federal prosecutors across the country.

Although the directive issued by Attorney General Eric Holder will apply nationwide, it will largely affect the 20 states and the District of Columbia that allow for medical marijuana use, and Colorado and Washington where state laws allow medical and recreational use by adults.

Holder briefed the governors of Colorado and Washington earlier Thursday on the new directive in a conference call. Federal prosecutors were expected to begin briefing authorities in other states later Thursday.

The new guidelines do not change marijuana's classification as an illegal drug. But it effectively discourages the pursuit of individual non-violent marijuana users who have no links to criminal gangs or cartel operations.

The document contains a list of eight new federal enforcement priorities, which is expected to guide federal authorities when weighing decisions on marijuana prosecutions. It also notified state authorities that the federal government reserved the right to intervene if the states did not enact appropriate regulations to protect federal interests, including guarding against the distribution of marijuana to minors.

The sweeping directive was described as a major breakthrough by advocates for decriminalizing marijuana use.

"Today's announcement demonstrates the sort of political vision and foresight from the White House we've been seeking for a long time,'' said Ethan Nadelmann, executive director of the Drug Policy Alliance, which supports the legalization of marijuana and favors referring offenders to treatment rather than prison.

"They (federal officials) are basically saying to Washington and Colorado: proceed with caution. They are giving (states) a chance to roll this out. This is politically and historically significant.''

Dan Riffle, the Marijuana Policy Project's director of federal policy, said it was now time "for Congress to act.''

"Today's announcement is a major and historic step toward ending marijuana prohibition,'' Riffle said. "The Department of Justice's decision to allow the implementation of the laws in Colorado and Washington is clear signal that states are free to determine their own policies with respect to marijuana.''

As recently as last week, the Obama administration signaled its approval for more lenient marijuana enforcement.

"While the prosecution of drug traffickers remains an important priority, the president and the administration believe that targeting individual marijuana users, especially those with serious illnesses and their caregivers, is not the best allocation of federal government resources,'' White House spokesman Josh Earnest said last Wednesday.

In Colorado, marijuana advocates said the announcement sent a reassuringly "strong signal" to state voters who in 2000 permitted medical marijuana for medicinal use, and then last fall approved recreational use.

Sen. Mark Udall, D-Colo., said he had long pressed the federal government to "respect the will of Colorado's voters.''

"This is a critical first step in providing much-needed certainty for Colorado's residents and businesses who have been left in limbo since the voters decriminalized marijuana in 2012," Udall said.

Attorney General John W. Suthers says the federal decision means Colorado can continue developing a marketplace for people to buy and sell legal pot. "As belated as it is, it's a welcome document. We now know what the ground rules are," Suthers says.

The Justice Department announcement, however was not being hailed in all corners.

"We are very disappointed that Eric Holder's not doing his job,'' said Calvina Fay, executive director of the Drug Free America Foundation. "It is his job to enforce our nation's laws.

"He has created what will become a tsunami that will most likely result in far too many young people becoming victims of chemical slavery,'' she said. "And it's really unforgivable. â?¦ He should be fired."

Peter Bensinger, former administrator of the Drug Enforcement Administration, said Holder's action amounted to a violation of the law.

"He's not just abandoning the law,'' Bensinger said, "he's breaking the law...He's putting the people of Washington and Colorado at risk. He's violating the treaty obligations of this country. He's telling the world we don't really follow the law here."

According to the new directive, federal authorities still will prosecute individuals or entities involved in:

The distribution of marijuana to minors.

Directing revenue from marijuana sales to gangs and cartels.

Diverting marijuana from states where it is legal to other states where there are no laws allowing for marijuana use.

Using legal sales as cover for trafficking operations.

Using violence and or firearms in marijuana cultivation and distribution.

Driving under the influence of marijuana.

Growing marijuana on public lands.

Possessing marijuana or using on federal property.

Senate Judiciary Committee Chairman Patrick Leahy, D-Vt., said he "welcomed'' the guidance that has been "long-awaited and in short supply.''

"The Justice Department should focus on countering and prosecuting violent crime, while respecting the will of the states whose people have voted to legalize small amounts of marijuana for personal and medical use,'' Leahy said.